The invention relates to automotive and light truck wheel suspension, specifically to that of retrofitting an existing coil spring based Mac Pherson strut and/or a standard coil over strut wheel suspension. This enables the strut to house an air spring where as vehicle height and spring rate is adjustable based on driver preference and/or road conditions.
Vehicles often are originally equipped from the manufacturer with wheel suspensions comprised of fluid shock absorber struts in conjunction with coil spring, that are used for suspension of vehicle weight, absorb variation in road surface, vehicle inertia, and to maintain a predesigned vehicle ride height. In some applications, an air spring is used in the original strut suspension design to compensate for the transverse load the strut experiences during jounce and rebound, and also acts to determine a preset ride height and spring rate. In U.S. Pat. No. 4,778,198, it is disclosed that an air spring is mounted substantially eccentric to the strut center line in order to compensate for transverse loading of the strut piston rod caused by jounce and rebound of the wheel. In U.S. Pat. No. 4,911,416, it is also disclosed that an air spring can be mounted eccentrically, offset, or at an angle to the strut axis, the air spring can be cut at a place oblique to the shock axis, all in order to compensate for the transverse loading previously described. In U.S. Pat. Nos. 4,668,774/4,998,082 and 5,129,634 it is also disclosed that an air spring is mounted in such fashion as to compensate for side load. By and large the disclosures of these patents and the use of air springs installed on telescoping shock-absorbing struts are intending to solve the problem of binding by the piston rod with in the shock absorber body.
They intend for an air spring to be a part of the initial strut design to eliminate various problems inherent in a coil spring suspended vehicle. These patents do not, however, make provisions for retrofitting a strut that is originally designed to utilize a coil spring, to an air spring design. Vehicles currently in circulation would require significant modification to utilize any of the above patents. A better design would be to allow a simple modification of an existing strut to house an air spring and require no other modification to the vehicle inner fender structure or upper strut mounting location. The only modification necessary would be to simply exchange a coil spring strut with an air ride retrofit strut of similar design.
Another aspect of air spring suspension known to those in the art is the ability to compensate for increased suspension load by various means and to vary spring rate according to vehicle sensed road conditions including but not limited to road surface variations, cross winds, and vehicle payload variations. In U.S. Pat. No. 5,060,959, a system using an air or coil spring in conjunction with an electrical motor to change ride height and or spring rate based on data received from a multitude of sensors located on moving suspension members. A computer system controls the input necessary for the actuators to change ride height and or spring rate. The computer determines the correct ride height and spring rate based on programmed variables and input from sensors.
Other U.S. patents including but not limited to U.S. Pat. Nos. 4,386,791 and 4,592,540 seek to offer variable dampening or spring rate due to road conditions or other dynamic factors acting upon the vehicle. These do not however, allow the driver to infinitely control the ride height or spring rate based on the drivers preferred road feel, handling characteristics, and also do not allow the driver to control ride height based on aesthetic preference. Most of these are controlled by other means such as computers or devices that are precalibrated. A better design for drivers who wish to be in command of ride height or spring rate would be one that is solely controlled by the driver from inside the passenger compartment.
This invention embodies a Mac Pherson strut or a standard coil over strut originally equipped with a coil spring seat located on the strut body and a system of variable dimension mounting plates and air springs. The invention seeks to allow automobiles currently equipped with a coil spring over strut style suspension to be retrofit with an air spring strut suspension. This invention also seeks to allow the driver to control the ride height and spring rate based on individual preference. To retrofit an air spring onto a Mac Pherson strut or a standard coil over strut already equipped with provisions for a coil spring; the strut must be properly prepared for the air spring assembly. The air spring assembly must be designed to have an airtight seal on the strut body and on the piston rod. It must also achieve the desired dimensions for the air bellows to operate within the designed extension and compression. The specifics of this design will be easily understandable when the description of the preferred embodiment is reviewed.